Control apparatus



Sept. 18, 1956 CONTROL SWITCH F. e. ADAMS ET AL 2,763,750

CONTROL APPARATUS File,d Dec. 31, 1953 LINE 20 2| 24 2s A I Y I LOAD w as 32 /|o l4 INVENTORS' FREDERiCK a ADAMS WILLIAM E. MARSHALL BY W C wax w ATTORNEY United States Patent CONTROL APPARATUS Frederick G. Adams, St. Louis Park, and William E.

Marshall, Minneapolis, Minn., assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application December 31, 1953, Serial No. 401,678

7 Claims. (Cl. 200122) The present invention is concerned with a control apparatus and in particular with a control apparatus to provide a controlling operation a given time interval after a control operation has occurred. More specifically, the present invention is concerned with a thermal timer in which a delayed switching function or the like is performed a given time interval after the thermal timer is energized.

In prior devices of this type, the timing interval has not been independent of line voltage variation and if accurate timing is desired it is necessary to provide a regulated supply of voltage from which the thermal timer can be energized.

Other prior art devices make use of a timer which has a short heating period and a long cooling period, with the timing interval including both the heating and the cooling period. In this way the timing interval is made less dependent upon line voltage variation. However, a variation in line voltage eifects the heating period and therefore the overall timing interval. Here again, for very accurate timing intervals it was necessary to provide a regulated supply of voltage.

It is the purpose of the present invention to provide an improved control apparatus wherein a time delay interval is provided which is independent of line voltage variation.

It is a further object of the present invention to provide a control apparatus having first and second bimetal elements arranged to control switch means and having a heater associated with one bimetal to heat the bimetal in accordance with line voltage and a second heater associated with the other bimetal to heat the other bimetal upon start of a timing interval, after which the switch means is actuated.

It is still a further object of the present invention to provide a control apparatus having first and second bimetal elements arranged to move in the same direction upon a change in ambient temperature with the first and second bimetal element controlling control means in accordance with the relative position of the first and second bimetal elements, to thereby give ambient temperature compensation, and having a first heater connected continuously to a source of power and heating the first bimetal in accordance with the line voltage, and having a second heater associated with the second bimetal to be energized from the line voltage upon the start of the timing interval, to thereby give a timing interval which is independent of ambient temperature and independent of line voltage variation.

These and other objects of the present invention will be apparent to those skilled in the art upon reference to the specification, claims, and drawing, of which the single figure is a diagrammatic and schematic representa tion of the improved control apparatus.

Referring to the single figure, the reference numerals 10 and 11 refer to a first and a second bimetal element which are rigidly fixed at one end to a base 12, the base 12 shown as being partially broken away. The bimetal 2,763,750 Patented Sept. 18, 1956 elements 10 and 11 may take various shapes, however, for the purpose of simplicity they have been shown as straight blades of bimetal. These bimetal elements must have the same deflection characteristics, that is, the bimetal elements 10 and 11 must flex to a like degree upon like changes in ambient temperature. Also, the bimetal elements 10 and 11 are mounted on the base 12 in a manner so that they flex in the same direction upon a given change in ambient temperature. This has been indicated on the figure by means of an arrow associated with each of the bimetal elements indicating that as the temperature rises the bimetal elements flex to the left.

The reference numeral 13 designates a latch member which is pivoted on the upper end of the bimetal 11 and is latched on the upper end of the bimetal 10. The latch member 13 is biased by means of spring 14 which is under tension and connects the latch member 13 to the base member 12. Also mounted on the latch member 13 is a normally closed switch 15.

Associated in heat conducting relationship to the bimetal 11 is a heater 16 which is effective to heat the bimetal 11 to a temperature above ambient temperature upon heater 16 being energized. Associated with the bimetal 10 is a further heater 17 which is located in heat conducting relationship to the bimetal 10 and is effective to heat bimetal 10 to a temperature above ambient temperature upon heater 17 being energized.

Electrical power is supplied to the control apparatus by means of conductors 20 and 21. With the apparatus as shown in the drawing, power is now applied to the conductors 20 and 21 and therefore the heater 16 is energized. This can be seen by tracing an energizing circuit for heater 16 from power line conductor 21 through condoctor 22, heater 16, conductor 23, and conductor 24 to the other power line conductor 20. Therefore, with the control apparatus as shown in the single figure, the bimetal 11 is heated to a temperature above ambient temperature and the bimetal 10 is at ambient temperature.

The ambient temperature which surrounds the bimetal elements 10 and 11 aflects these two elements in a like manner. However, the temperature of the bimetal element 11 depends not only upon ambient temperature but also upon the power being dissipated by heater 16. It can be readily seen that the power dissipated by heater 16 is dependent upon the magnitude of the line voltage present at the power line conductors 20 and 21. If the line voltage should drop, less power will be dissipated in heater 16 and the temperature of the bimetal 11 will decrease. This will cause bimetal 11 to move to the right. Also, if the voltage present at the power line conductors 20 and 21 should increase, the power dissipated in heater 16 will increase and the bimetal 11 will move to the left.

Since the latch member 13, which is latched on the upper end of bimetal 10, is pivoted on the upper end of bimetal 11, the position of the latched end of the latch member 13 with respect to the bimetal 10 depends upon the temperature of the bimetal 11 which in turn depends upon the magnitude of the line voltage present at the power line conductors 20 and 21.

To initiate a timing interval, a control device 30 is actuated to control an energizing circuit for heater. 17. Control device 30 may be a control switch, shown as a manual switch, this switch can be responsive to a great many conditions such as pressure or temperature. The energizing circuit for heater 17 can be seen by tracing a circuit from power line conductor 21 through conductor 31, control switch 30, conductor 32, heater 17, and conductor 33 to the other power line conductor 20.

Energization of heater 17 causes this heater to dissipate power which raises the temperature of bimetal 10. The rate with which bimetal 10 is heated, that is, the rate at which the temperature of the bimetal'in- 3 creases, is dependent upon the power which is dissipated in the heater 17. This is likewise dependent upon the magnitude of the voltage applied to the power line conductors 20 and 21.

Ifit is assumed that the power line voltage is low it will be remembered that the heater 16 is dissipating less power and therefore the bimetal 11 and the latch member 13 move to the right. This means that bimetal It? will have to move a shorter distance to the left to unlatch the latch member 13. Therefore, while heater 17 is energized from a low line voltage the bimetal i has a smaller distance through which it must move to perform thereforehave to move a greater distance to unlatch the 'latch member 13. However, this greater movement would be accomplished in the same time interval since more power is dissipated in the heater 17 due to the abnormally liigh line voltage.

The timing interval of the control apparatus can be defined as the time interval between the closing of the control device 3 and the unlatching of the latch member 13, While the unlatching of the latch member 13 can perform a variety of functions it has been shown for the purpose of simplicity as controlling a normally closed switch 15. This normally closed switch 15 is in series with a load 4%) which is normally continuously energized from the power lines 2 and 21. This can be seen by tracing a circuit from power line conductor 21 through conductor 41, load iii, conductor 42, switch 15,'conductor 43, and conductor 24 back to power line interval being independent of variation of the line voltage 'appliedto the power line conductors 20 and 21.

Assume now that a power failure occurs and that heater .16 cools. Bimetal element 21 will then return to ambient temperature and will to the right. in the particular modification shown, the length of the latch element 13 is such that thelatch element 13 will be unlatched .from, the upper end of bimetal it? upon the cooling of'birnetal element 11 to ambient temperature. This will open switch 15and if the control device 3% is closed before power is again applied to the power line conductors 20 and 21 the timing interval will not result until the heater 16 .has heated bimetal element 11 and the latch element '13 is reset or again latched on the end of bimetal 10.

For purposes of simplicity, a reset means for the latch element 13 has not been shown. However, it is within the scope of the present invention to provide any one of a number of known manual reset or automatic reset means for resetting the latch element 13.

It is also within the scope of the present invention to provide a device wherein the latch element 13 will not be unlatched from bimetal element upon a power failure.

From the above description it can be seen. that we have provided an improved control apparatus giving a timing function which is independent of line voltage variation.

We claim as our invention:

1. Control apparatus comprising; a base member, first and second bimetal elements mounted on said base memher in a manner to move in like directions with respect to said basemember upon like temperature. changes of saidbimetal elements, switch means controlled in accordance with the relative positions of said first and second bimetal elements, a source of power, a first heater associated with said first bimetal element, circuit means connecting said first heater directly to said source of power to thereby continuously energize said first heater, a second heater associated with said second bimetal element, control means, and circuit means including said control means connecting said second heater to said source of power to thereby actuate said switch means a predetermined time period after said circuit means is completed.

2. Voltage and temperature compensated time delay apparatus comprising; a first and a second bimetal element each having a first end rigidly mounted to a base member, a latch element pivoted at the other end of one of said bimetal elements and latched at the other end of the second of said bimetal elements, said latch element being unlatched from the other end of said second of said bimetal elements upon predetermined relative movement between said first and second bimetal elements, said first and second bimetal elements moving in like directions upon a change in ambient temperature so that no relative movement takes place between said bimetal elements due to change in ambient temperature, a source of electrical power, a first heater associated with said first bimetal element to heat said element when said first heater is energized, circuit means continuously connecting said first heater to said source of power to thereby heat said first bimetal element in accordance with the voltage level of said source of power, a second heater associated with said first bimetal element to heat said element when said second heater is energized, control means, and circuit means including said control means in circuit closing condition connecting said second heater to said source of power.

3. Control apparatus comprising, a base member, first and second bimetal elements fixed to said base member, control means actuated upon relative movement of said first and second bimetal elements, a source of electrical power, a first heating element associated with said first bimetal element to heat said first bimetal element when said first heating element is energized, circuit means continuously connecting said first heating element to said source of power to thereby heat said first bimetal element, and a second heating element associated with said second bimetal element to heat said second bimetal element upon said second heating element being connected to said source of power.

4. Control apparatus comprising, a base member, a first and a second heat responsive member mounted on said base member and arranged to move relative to each other only when the temperatures of said first and second heat responsive members differ, first means for heating said first heat responsive member upon energization of said first means by a source of power, second means for heating said second heat responsive member upon encrgization of'said second means by a source of power, a source of electrical power, means continuously connecting said first means to said source of power, control means, means including said control means connecting said second means to said source of power, and means controlled by relative movement between said first and second heat responsive members.

5. Control apparatus comprising, first temperature responsive means responsive to ambient temperature and having electrically energizable heating means, a source being in circuit closing condition, and means controlled jointly by said first and second temperature responsive means.

6. Voltage compensated timing control apparatus comprising, first temperature responsive means having a first movable bimetal element and a first electrically energizable heater for said first bimetal element, a source of electrical voltage, circuit means continuously connecting said first heater to said source of voltage to thereby heat said first bimetal element and cause it to assume a first position indicative of the voltage level of said source of voltage, second temperature responsive means having a second movable bimetal element and a second electrically cnergizable heater for said second bimetal element, control means, and circuit means including said control means connecting said second heater to said source of power to thereby heat said second bimetal element and cause it to move from a first to a second position at a rate dependent upon the voltage level of said source of voltage, and means controlled by said first and second bimetal elements in a first manner when said first and second bimetal elements are in said first position and in a second manner when said second bimetal element moves to said second position.

7. Control apparatus comprising; first heat responsive means having a first movable bimetal element and a first heater, a source of power, means continuously connecting said first heater to said source of power, second heat responsive means having a second movable bimetal element and a second heater, said first and second bimetal elements being arranged to move in like directions upon a like change in temperature of said bimetal elements, a latch member pivoted on one of said bimetal elements and latched on the other of said bimetal elements, a normally open control switch, circuit means including said control switch connecting said second heater to said source of power upon said control switch being closed to thereby heat said second bimetal and cause it to move so that said latch member is unlatched a time period after said control switch is closed.

References Cited in the file of this patent UNITED STATES PATENTS 2,306,810 Jones Dec. 29, 1942 2,329,119 Jacobs Sept. 7, 1943 2,535,969 Tramontini Dec. 26, 1950 

